This invention provides a display device that responds to, and locates, a touch at essentially any location on a faceplate that overlies the display.
The invention can be used with various display devices of the type which display a number of information items and from which a viewer is to make a selection. One example is a juke box which displays a number of recorded song titles, and a user selects the titles which are to be performed. Another example is an index which accompanies a map, and which illuminates on the map those locations which a user selects. A further example is user selection of information items displayed on the screen of a cathode-ray tube (CRT) terminal that is connected with a computerized information system.
CRT display terminals are known which respond to touch at any of a selected pattern of locations on the display screen. These terminals typically employ a pattern of transparent contacts over the display screen. The terminal responds to touch at any contact in the prescribed pattern and identifies the location of the touched contact. Examples of touch terminals of this nature are disclosed in U.S. Pat. No. 3,696,409 and in the co-pending and commonly assigned U.S. applications for patent Ser. No. 170,056 filed July 18, 1980 and Ser. No. 259,614 filed May 1, 1981.
Another known practice employs a pattern of transparent mechanical switches over a display. Sierracin/Intrex Products in Sylmar, Calif. markets Transflex (.TM.) brand switches of this type.
It has also been proposed to detect and to locate the touch of a display screen by providing an array of optical sources and detectors around the periphery of the display screen. One alternative is to provide an array of sonic generators and sonic detectors around the periphery of the display screen. In each instance, the sources and detectors are connected with an electronic system that responds to and locates the disturbance which a touch causes in the unbounded spatial energy field. Examples of this and related art include U.S. Pat. No. 4,198,623 and the patents noted therein.
An object of this invention is to provide an improved touch-responsive unpatterned display device. The term "unpatterned" is used herein to characterize a touch-responsive display device that can detect and locate a touch at a location anywhere on the display screen, in contrast to selecting one location from a prescribed set of locations having known, i.e. patterned, locations.
A further object is to provide such a display device that determines the position of a touch without use of an unbounded spatial energy field.
A more particular object is to provide a touch-responsive unpatterned display device that determines the position of a capacitive touch on an electrically-conductive film overlying the display screen.
It is also an object that the display device locate a touch with relatively high reliability.
Another object is to provide a display device of the above character that determines the position of a touch with relatively small spatial ambiguity, that is, with relatively good accuracy and precision.
A further object is to provide a display device of the above character suited for relatively low cost manufacture.
Other objects of the invention will in part be obvious and will in part appear hereinafter.